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21.
Summary Over three years of study, small plants of Cynoglossum officinale consistently produced more flowers per unit of dry weight than large plants. In contrast to earlier results, weight of all seeds tended to increase more than proportional to size. As a result a positive correlation existed between seed set per flower and plant size. The correlation between the mean number of pollinator visits per flower and size was positive but not significant. In a field experiment we found that resources rather than pollen were limiting seed set. Thus, it is unlikely that enhanced pollination of the largest plants causes the size-dependency of seed set per flower. Alternative hypotheses are discussed briefly.Publication of the Meijendel Comité, New Series No. 96 相似文献
22.
This work provides further evidence that plants contain appreciable amounts of inorganic pyrophosphate (PPi), and that breakdown of phosphoribosyl pyrophosphate (PPRibP) does not contribute significantly to the PPi detected in plant extracts. Inorganic pyrophosphate in extracts of the roots of Pisum sativum L., clubs of the spadices of Arum maculatum L., and the developing endosperm of Zea mays L. was assayed with pyrophosphate fructose 6-phosphate 1-phosphotransferase (EC 2.7.1.90), and with sulphate adenyltransferase (EC 2.7.7.4). The two different assays gave the same value for PPi content, and for recovery of added PPi. It was shown that PPRibP is converted to PPi during the extraction of PPi. However, the amounts of PPRibP in clubs of A. maculatum and the developing endosperm of Z. mays were negligible in comparison with the contents of PPi.Abbreviations EDTA
ethylenediaminetetraacetic acid
- PFK(PPi)
pyrophosphate fructose 6-phosphate 1-phosphotransferase
- PPi
inorganic pyrophosphate
-
PPRibP
phosphoribosyl pyrophosphate 相似文献
23.
Summary Shin et al. (Biochim Biophys Acta 444: 794–801, 1976) described the subcellular location of [3H]folic acid after injection into rats. The microsomal fraction of the liver contained relatively large amounts of tracer initially but lower amounts at later times. Because of the heterogeneous nature of the microsomal fraction of the liver we re-examined the nature of the folate binding fraction. The location of injected [3H]folic acid resembled that of the microsomes derived from the plasma membrane, where ultracentrifugal analysis was conducted in the presence and absence of cesium ions. The location of the folate did not resemble that of microsomes derived from the endoplasmic reticulum (ER). One of the marker enzymes of the ER was the vitamin K-dependent carboxylase. A simple method for reducing vitamin K is described. 相似文献
24.
The distribution of excreted flavonoid aglycones within the familyLabiatae was studied and differences were found, especially in the A-ring substitution patterns. Thus, 5,7-dihydroxy-6-methoxyflavones with substituted B-rings are characteristic of species ofSalvia (sect.Salvia),Rosmarinus andOcimum; 5,7-dihydroxy-6,8-dimethoxyflavones occur only inOcimum and 5,6-dihydroxy-7,8-dimethoxyflavones inThymus and related species. Members of the two subfamiliesLamioideae andNepetoideae produce exudate flavonoids, but some genera are devoid of these compounds. There is a correlation between the habitat where the plant grows and production of these compounds, the species from (semi-)arid habitats being those which generally accumulate external flavonoids. 相似文献
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Catharina Larsson Günther Weber Eva Kvanta Kathy Lewis Marie Janson Carol Jones Tom Glaser Glen Evans Magnus Nordenskjöld 《Human genetics》1992,89(2):187-193
Summary Multiple endocrine neoplasia type 1 (MEN1) is characterized by neoplasia of the parathyroids, the pancreas, and the pituitary. Tumorigenesis involves unmasking of a recessive mutation at the MEN1 locus, which has been mapped to the centromeric part of chromosomal region 11q. In order to localize the MEN1 gene further and to make its isolation possible, a number of new markers were isolated. Two radiation-reduced somatic cell hybrids were identified that only contained markers close to and flanking the MEN1 region. DNA from these hybrids was used for the construction of a cosmid library, and clones containing human inserts were isolated. In addition, cosmid clones were isolated for locus expansion of 7 other markers that were mapped to the 11q12–13.2 region. The 33 newly isolated clones together with 25 previously published markers from this region were analyzed in a panel of radiation-reduced somatic cell hybrids. From the hybridization pattern, the region was divided into 11 parts. New restriction fragment length polymorphisms were identified in 7 of the newly isolated cosmid clones and in one plasmid. These were then used to sublocalize meiotic cross-overs more precisely in two MEN1 families, thus refining the mapping of the disease gene. 相似文献
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29.
The P gene of human parainfluenza virus type 1 encodes P and C proteins but not a cysteine-rich V protein. 总被引:17,自引:11,他引:6
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Y Matsuoka J Curran T Pelet D Kolakofsky R Ray R W Compans 《Journal of virology》1991,65(6):3406-3410
The nucleotide sequence of the P gene of human parainfluenza virus type 1 (PIV1) was determined from cloned cDNA copies of the mRNA. By analogy with the gene organization of Sendai virus, two open reading frames in the mRNA sense of the gene were identified as coding sequences for the P protein (568 amino acids with an estimated molecular weight of 64,655) and the C protein (204 amino acids with an estimated molecular weight of 24,108). Comparison of the deduced amino acid sequences of the P and C proteins of PIV1 with those of Sendai virus showed a high degree of homology. However, a sequence for the cysteine-rich V protein, which was considered a common feature of other paramyxoviruses, was interrupted by the presence of multiple stop codons. The sequence analysis of three P-gene-specific cDNA clones generated from genomic RNA by polymerase chain reaction and one additional clone generated from mRNA confirmed that the coding sequence for the cysteine-rich region is silent in the PIV1 gene and thus is not translated into protein. Two potential editing sites with the consensus sequence 3'UUYUCCC were found in the PIV1 P gene at positions 564 to 570 and 1430 to 1436. However, examination of the PIV1 mRNA population by a primer extension method indicated that neither of these sites is utilized. These results indicate that the PIV1 P gene has a coding strategy different from those of other paramyxovirus P genes. 相似文献
30.
We have partially characterized root hydrotropism and its interaction with gravitropism in maize (Zea mays L.). Roots of Golden Cross Bantam 70, which require light for orthogravitropism, showed positive hydrotropism; bending upward when placed horizontally below a hydrostimulant (moist cheesecloth) in 85% relative humidity (RH) and in total darkness. However, the light-exposed roots of Golden Cross Bantam 70 or roots of a normal maize cultivar, Burpee Snow Cross, showed positive gravitropism under the same conditions; bending downward when placed horizontally below the hydrostimulant in 85% RH. Light-exposed roots of Golden Cross Bantam 70 placed at 70° below the horizontal plane responded positively hydrotropically, but gravitropism overcame the hydrotropism when the roots were placed at 45° below the horizontal. Roots placed vertically with the tip down in 85% RH bent to the side toward the hydrostimulant in both cultivars, and light conditions did not affect the response. Such vertical roots did not respond when the humidity was maintained near saturation. These results suggest that hydrotropic and gravitropic responses interact with one another depending on the intensity of one or both factors. Removal of the approximately 1.5 millimeter root tip blocked both hydrotropic and gravitropic responses in the two cultivars. However, removal of visible root tip mucilage did not affect hydrotropism or gravitropism in either cultivar. 相似文献